Update - since birth its highly likely she only ever had one kidney and been fine without one. The issue has been with her ureter being instructed and unable to work between her kidney and bladder.
She had surgery overnight to put in a sub device that essentially acts as a ureter, which was successful and will need flushing every 3-4 months. Waiting for a call today to see how she's getting on and take it from there. Essentially, they want her to produce urine.
Insurance will cover a decent chunk, but not all of it, and we've put down a deposit. Think a lot of people would have said it's time to say goodbye but we love her so much even after having her for such a short period of time we're determined to not give up on her.